1. Field of the Invention
This invention relates to the preparation of organic isocyanates, and, more particularly, is concerned with the preparation of novel araliphatic diisocyanates.
2. Description of the Prior Art
Organic diisocyanates find particular utility in the preparation of polyurethane plastics, particularly elastomeric polyurethanes used in the production of fibers, films, and various cast and formed articles. The art has long recognized the problems which arise with respect to the color stability, and, even mechanical properties, upon ageing, of those urethanes containing aromatic diurethane linkages. For example, a clear colorless polymer when exposed to the action of sunlight, or equivalent ultraviolet irradiation, will change to yellow then to amber, and on extensive exposure even to a brown. Mechanical property losses generally occur concurrently with the color changes.
In contrast, those urethanes prepared from aliphatic, cycloaliphatic, or araliphatic diisocyanates, generally speaking, provide for enhanced polyurethane stability, especially in regard to color stability as well as mechanical property retention. This phenomenon is widely recognized and amply documented by C. S. Schollenberger and F. D. Stewart, J. Elastoplastics 4, 294 (1972).
We have now found a novel class of araliphatic diisocyanates which are particularly useful for the preparation of light stable polyurethane polymers and which are easily prepared from readily available and economically attractive starting materials.
Related aryl(isothiocyanatoalkoxylates) have been reported as useful for fungicides and anthelmintics; see U.S. Pat. Nos. 3,198,821 and 3,342,846. However, the prior art has not recognized the analogous oxygen compositions for their ability to provide color stable polyurethane products which is an object of the present invention.